Master Python Control Flow: If, For, While Explained with Real Examples

If Statement

The if statement lets you execute a block of code only when a specific condition is true. An optional else clause handles the opposite case.

# if statement executes a block when the condition is met.
age = 18
if age >= 18:
    print("You are an adult.")
else:
    print("You are a minor.")

Multiple conditions can be chained with elif to cover several ranges.

# multiple condition checks
score = 85
if score >= 90:
    print("Grade A")
elif score >= 80:
    print("Grade B")
else:
    print("Grade C")

For Loop

The for loop iterates over each element in a sequence such as a list, tuple, or string.

# iterate over a list of fruits
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

It can also iterate over a string character by character.

# iterate over a string
for letter in "hello":
    print(letter)

While Loop

The while loop repeats as long as a condition remains true. It is useful for situations where the number of iterations isn’t known in advance.

# while loop runs while the condition is true
count = 0
while count < 5:
    print(count)
    count += 1

A common pattern is an infinite loop with a break condition.

# break out of an infinite loop
number = 1
while True:
    print(number)
    number += 1
    if number > 10:
        break

Combined Use Cases

By nesting if statements inside loops, you can create more sophisticated logic.

# filter even numbers
numbers = [1, 2, 3, 4, 5]
for num in numbers:
    if num % 2 == 0:
        print(num)

Accumulate values until a target is reached using a while loop.

# accumulate until total reaches 100
total = 0
num = 1
while total < 100:
    total += num
    num += 1
print(total)

Combine functions, loops, and conditionals to solve algorithmic problems, such as finding the first prime number.

# find the first prime number
def is_prime(n):
    if n <= 1:
        return False
    for i in range(2, n):
        if n % i == 0:
            return False
    return True

number = 2
while True:
    if is_prime(number):
        print(f"The first prime number is {number}")
        break
    number += 1

Understanding these control‑flow constructs is essential for building flexible and intelligent Python programs.